Predatory Bacteria Attenuate Klebsiella pneumoniae Burden in Rat Lungs.

Kenneth Shatzkes,Shilpi Gupta,Joseph Rinaggio,Sean Shukla,Michael Zuena,Daniel E Kadouri,Eric Singleton,Sonal Dharani,Onoyom Onyile,Chi Tang,Nancy D Connell,Eric J Rubin,Babak Javid

doi:10.1128/mbio.01847-16

Abstract

ABSTRACTBdellovibrio bacteriovorus and Micavibrio aeruginosavorus are predatory bacteria that naturally—and obligately—prey on other Gram-negative bacteria, and their use has been proposed as a potential new approach to control microbial infection. The ability of predatory bacteria to prey on Gram-negative human pathogens in vitro is well documented; however, the in vivo safety and efficacy of predatory bacteria have yet to be fully assessed. In this study, we examined whether predatory bacteria can reduce bacterial burden in the lungs in an in vivo mammalian system. Initial safety studies were performed by intranasal inoculation of rats with predatory bacteria. No adverse effects or lung pathology were observed in rats exposed to high concentrations of predatory bacteria at up to 10 days postinoculation. Enzyme-linked immunosorbent assay (ELISA) of the immune response revealed a slight increase in inflammatory cytokine levels at 1 h postinoculation that was not sustained by 48 h. Additionally, dissemination experiments showed that predators were efficiently cleared from the host by 10 days postinoculation. To measure the ability of predatory bacteria to reduce microbial burden in vivo, we introduced sublethal concentrations of Klebsiella pneumoniae into the lungs of rats via intranasal inoculation and followed with multiple doses of predatory bacteria over 24 h. Predatory bacteria were able to reduce K. pneumoniae bacterial burden, on average, by more than 3.0 log10 in the lungs of most rats as measured by CFU plating. The work presented here provides further support for the idea of developing predatory bacteria as a novel biocontrol agent.

Highlights

Bdellovibrio bacteriovorus and Micavibrio aeruginosavorus are predatory bacteria that naturally—and obligately— prey on other Gram-negative bacteria, and their use has been proposed as a potential new approach to control microbial infection
While the safety of administering predatory bacteria into the lungs of mice has already been demonstrated [19], we began by investigating if the predators are compatible with the animal model being used in this study, Sprague-Dawley (SD) rats
To examine the effect on host morbidity of introducing predatory bacteria into the respiratory tract of SD rats, we performed intranasal inoculations of 6.0 ϫ PFU/rat of B. bacteriovorus 109J, 1.1 ϫ PFU/rat of B. bacteriovorus HD100, or 5.0 ϫ 107 PFU/rat of M. aeruginosavorus ARL-13 into rats in three groups containing six rats each. Another group of six rats was inoculated as a control with the vehicle, phosphate-buffered saline (PBS)

Summary

Introduction

Bdellovibrio bacteriovorus and Micavibrio aeruginosavorus are predatory bacteria that naturally—and obligately— prey on other Gram-negative bacteria, and their use has been proposed as a potential new approach to control microbial infection. We report one such new approach: the use of predatory bacteria (Bdellovibrio bacteriovorus and Micavibrio aeruginosavorus) that naturally—and obligately—prey on other Gram-negative bacteria To our knowledge, this is the first study that demonstrated the ability of predatory bacteria to attenuate the bacterial burden of a key human pathogen in an in vivo mammalian system. The issue of MDR infections and the lack of antibiotics in the development pipeline have spurred researchers to consider new ways to combat bacterial infection in the coming postantibiotic era One such approach is the use of naturally occurring predatory bacteria. No of rats showing visual signs of morbidity at indicated time after inoculation/total no. of rats

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